1. Field of the Invention
This invention relates to an apparatus for plasma treatment capable of operating as a part of systematized unit when a filtration membrane module thereof is properly connected to any of centrifugal separators of two kinds different from each other in performance mechanism. By means of such a systematized unit as above, pathogenic substances and harmful substances as immunocompounds, immunoglobulin association, and nucleic acid contained in blood can efficiently be removed.
2. Description of Prior Art
It has become apparent recently that an abnormal increase in the quantity of high-molecular-weight substance is greatly causative of the origination and conditions of various diseases such as: autoimmune diseases including rheumatism, SLE, myasthenia gravis, Goodpasture syndrome, and idiopathic thrombocytopenic purpura; abnormal metabolism including multiple myeloma and macrogobulinemis; and hyperviscosity syndrome; whereby plasmapheresis has come into wide use for the purpose of removing high-molecular-weight substances. Plasmapheresis is a process to separate blood into plasma and a corpuscular fraction first, remove harmful high-molecular-weight substances from separated plasma component, and then return treated plasma component thus treated together with previously separated corpuscular fraction to the patient's body.
Among conventional methods of separating blood into plasma and a corpuscular fraction, there has been a membrane separation method using a filtration membrane module and a centrifugal separation method using a centrifugal separator. Known methods of plasma separation using the membrane module include the following:
(1) A method wherein, after separating blood into plasma and a corpuscular fraction through plasma separation membrane, a plasma fraction containing harmful substances is removed and a fresh plasma fraction in quantity corresponding to that of the removed plasma fraction is mixed with corpuscular component and returned to the patient's body.
(2) A method wherein, after separating blood into plasma and a corpuscular fraction through plasma separation membrane, a plasma fraction containing harmful substances is brought into contact with adsorbent so as to be adsorbed and removed thereby, and the plasma fraction thus treated is again mixed with corpuscular component and returned to the patient's body. (U.S. Pat. No. 4,013,564; U.S. Pat. No. 4,243,532)
(3) A method wherein, after separating blood into plasma and a corpuscular fraction through plasma separation membrane, plasma component is further separated into low-molecular-weight substances containing albumin and high-molecular-weight substances through plasma treatment membrane, and then purified plasma component free of high-molecular substances containing harmful substances is mixed with corpuscular component and returned to the patient's body. (U.S. Pat. No. 4,350,594; U.S. Pat. No. 4,397,747)
(4) A method wherein, after separating blood into plasma and a corpuscular fraction through plasma separation membrane, plasma fraction is cooled so that high-molecular-weight substances containing harmful substances are caused to gel, the produced gel is removed by filtration membrane, and only such low-molecular-weight substances as pass through the filtration membrane are returned to the patient's body after being mixed with corpuscular fraction. (Artificial Organs, Vol 4, No. 3, pp. 205-207, June, 1980.
On the other hand, the following methods are known as plasmapheresis depending on the centrifugal separation methods:
(1) A method wherein, after separating blood into plasma and a corpuscular fraction by means of centrifugal separator, plasma fraction containing harmful substances is removed and fresh plasma in quantity corresponding to that of corpuscular component is mixed with corpuscular component and returned to the patient's body.
(2) A method wherein, after separating blood into plasma and a corpuscular fraction by means of a centrifugal separator, plasma fraction is separated into high-molecular-weight substances and low-molecular-weight substances by the filtration membrane module and purified plasma from which high-molecular-weight substances alone are removed is returned to the patient's body together with corpuscular component. (Japan Laid-open Patent, Nos. 64,058/82 and 8,967/84.
Among said plasmapheresis methods, plasma exchange therapy is followed by a problem in securing healthy persons' plasma to be transfused into patients' bodies and also secondary effects such as infection caused by other kinds of pathogenic organisms or contraction of serum sickness occurring with transfusion of healthy person's plasma into the patient's body, and therefore transfusion of the patient's own purified plasma is regarded as preferable. Above all, a method of separating blood into plasma and a corpuscular fraction by means of a centrifugal separator and treating plasma fraction by the filtration membrane module is quite safe and excellent in that a fall in separation efficiency as a problem in separation of blood by the filtration membrane module and risky hemolysis are never caused. However, blood treatment by means of a system of combination of the centrifugal separator with the filtration membrane module is scarcely performed these days. The reason for the above fact is considered as follows:
Centrifugal separators in use today for plasma separation are of two kinds different from each other in performance mechanism, that is:
(1) An apparatus of continuous operation type in which blood is continuously fed into the centrifugal bowl at one side and corpuscular fraction and plasma are individually and continuously taken out from the bowl at the other side. (IBM 2,997: Travenol CS-3,000)
(2) An apparatus of batch type in which blood is fed into the bowl at one side and plasma fraction alone is continuously taken out from the bowl at the other side whereas corpuscular fraction is collected in the bowl until when blood letting is stopped immediately after corpuscular fraction sensing means senses corpuscular fraction overflowing the bowl and flowing into the plasma outlet tube, and then corpuscular fraction collected in the bowl are taken out from the blood feeding port. (Haemonetics V-50, Haemonetics PEX) In the case of connecting the centrifugal separator that has been used hitherto with a filtration membrane module, the control circuit of the centrifugal separator must be modified for using closed circuits each exclusive for the centrifugal separator or the module and adapting the control system of the centrifugal separator to control a pump to be connected to the filtration membrane module. Further, the use of exclusive closed circuits prevents the module from being connected to a centrifugal separator whose performance mechanism is different from that of the separator now in use.